Bleaching fibers and a composition therefor



Patented Feb. 6, 1940 UNITED STATES BLEACHING FIBERS AND A COMPOSITION THEREFOR Hans 0. Kaufl'mann, Eggertsville, N. Y., assignor to Buffalo Electro-Chemical Company, Inc" Buffalo, N. Y.

No Drawing. Application February 5, 1938, Serial No. 188,984

11 Claims.

The present invention relates to a composition and method for bleaching cellulose, whether natural or regenerated, particularly in the form of fibers and/or filaments. More particularly it relates to a composition and method for bleaching such fibers and/or filaments with alkaline solutions containing hydrogen peroxide at room temperature. The invention will be described with reference to filamentary material or to fabrics, etc, formed from filamentary material.

This application is a continuation in part of my copending application, Serial No. 714,735, filed March 8, 1934, Patent Number 2,107,297, patented February 8, 1938.

Heretofore, it has been deemed necessary, in

leaching cellulose with hydrogen peroxide, to employ relatively high temperatures together with expensive and cumbersome apparatus. In carrying out such processes it is necessary, in 0 order to avoid degradation of the cellulose, to use relatively low concentrations of both hydrogen peroxide and alkali.

In my present invention I am able to bleach cellulose readily and expeditiously with a minimum of equipment and without the necessity of prolonged immersion or heating. The bleached material obtained is of an exceptional whiteness and possesses in most cases enhanced physical properties such as greater tensile strength, better handle, and freedom from injury or tenderness. The material is left in excellent condition, heretofore thought impossible on a practical scale, since the action of the bleaching solution is effected at normal or room temperatures and this eliminates the catalytic effects which take place at elevated temperatures in peroxide solutions.

In accordance with my invention, the material may be preliminarily cleaned or treated accord- 40 ing to the usual known practices as for instance souring, scouring, desizing, boiling, desulphurizing, degurnming or other usual preliminary cleaning actions, or preliminarily treated with alkaline or acid hypochlorite solutions, hydrosulphites, and similar oxidizing or reducing agents. It is then treated with an alkaline solution of hydrogen peroxide at room or normal temperature by any method whereby the fabric or fiber whether as raw stock, yarn, Woven or knitted 5O goods, is thoroughly wet out or saturated with the desired bleaching solution. This step will usually include a saturation of the goods, such as by immersion or immersions in the bleaching solutions, and an elimination of the surplus bleaching solution above that necessary to saturate the same by any well known means as, for instance, by squeezing or hydroextracting or by any known device or method, or the goods are saturated by any other convenient methods and permitted to stand in the saturated condition until the desired bleached result is obtained. This desired bleached condition is obtained after a period of from several minutes or up to 24 hours or more whereupon the goods are rinsed or the residual solution otherwise removed. It will, of course, be understood that the surplus bleaching solution squeezed or hydroextracted from the goods may be returned to the main bulk of the bleaching solution and thereafter used to bleach further batches of goods.

To those who are acquainted with bleaching procedures, it will be understood that in some cases a preliminary treatment of the fiber is not necessary, as my process will be effective on fibers as they appear naturally or come from certain manufacturing processes without the preliminary cleaning or chemical treatment. The process is, however, particularly adapted for the treatment of gray cotton goods.

A composition of bath which I have found eifective in bleaching cellulose, whether in the raw state or as prepared goods, contains an alkali in addition to water and hydrogen peroxide. This alkali may include materials acting as stabilizers for the hydrogen peroxide solution and may include, among others, silicates of soda, phosphates such as sodium pyrophosphate, trisodium phosphate, di-sodium phosphate, sodium bicarbonate and borax. As the alkaline material it is preferred, however, to use the usual and wellknown alkaline substances used in bleaching operations such as caustic soda, soda ash, ammonia, etc. The quantity of alkaline material used should be considerably in excess of that considered permissible heretofore and when present as caustic soda should be between 10 and 60 grams per liter. When other alkaline materials are used in place of some or all of the caustic soda the total amount of alkali present should be such as to equal in alkalinity (require an equal amount as of acid to be neutralized) the above amount of caustic soda.

It will, of course, be understood that additional chemicals or stabilizers, not necessarily alkaline in character, may be added to the bath. Depending upon the type of material, its previous treatments and history, bleaching assistants may also be included in the bath and among them may be mentioned soaps, sulphonated oils, solvents of various kinds, and wetting-out agents.

As a typical example of a solution suitable for bleaching cellulose fibers or filaments is the following solution:

gals. water 5 to 25 lbs. silicate of soda 42 36. 10 gals. hydrogen peroxide, volume The goods are saturated with the bleaching solution, the surplus bleaching solution above that necessary to saturate the goods is removed, and the goods permitted to stand in the saturated condition until the desired degree of bleaching is effected. I have found that piece goods may be effectively bleached after saturation by winding them upon rolls. The saturated goods may be stacked, piled, or stored in any convenient manner in a box, bin or movable container or even on the floor of or in any suitable chamber. In this manner the goods are maintained damp during the bleaching procedure.

Effective hydrogen peroxide bleaching is very often obtained in accordance with my invention by subjecting the goods to a double treatment such as according to the following example:

The first steep is carried out with a solution containing 10 grams of caustic soda, 30 cos. of 42 B. silicate of soda, and 20 cos. of 100 vol. hydrogen peroxide per liter of aqueous solution. The goods are saturated with this'bleaching solution, the excess of the solution expressed or eliminated, whereby the goods retain from 50 to 130% or more of their original weight, or the goods saturated by any other convenient method. They are then permitted to stand in this saturated condition from 8 to 16 hours, although the time may fall without these limits depending upon the type of goods, concentration of the chemicals in the solution, and then rinsed and subjected to a second steep in a solution containing 20 grams of caustic soda, 60 ccs. of 42 B. silicate of soda, and 40 ccs. of 100 vol. hydrogen peroxide per liter of aqueous solution. The goods are saturated and treated in a manner similar to that described for the first steep, the steeping operation requiring 2 to 12 hours. The goods are then thoroughly rinsed with water and dried and finished in the usual manner.

Where the cellulose, such as in the form of gray cotton goods, contains a considerable amount of impurities such as motes, cotton seeds, stains, dirt and other undesirable foreign matter, the usual alkaline boil thought necessary may often be eliminated and good bleaching results obtained by steeping in the hydrogen peroxide solution described herein containing very high concentration of alkali equivalent to about 10 to 60 grams of sodium hydroxide per liter.

My process is adaptable for use in bleaching goods containing colored portions (cotton, linen, etc.) I have found in practical operation that ii the goods are given one or more treatments with a solution of the composition described above, the danger of bleeding or fading of colors is very considerably minimized.

Goods which have been mercerized may be bleached by my process without removing caustic soda remaining in the goods after they come from the mercerizing machines. This will also eliminate the usual souring of such goods.

In cases of linen, ramie, jute, artificial silk and other natural or regenerated vegetable fibers I have found a steep at room temperature effective wherever a hot prolonged boil with alkaline peroxide would formerly have been necessary to obtain a desirable bleach. I have found that my process eliminates many preliminary, intermediate or final steps, in the wet processing of cellulose.

The process is also adaptable to bleaching of wood and other pulp such as is used in the paper or related industries. It also is suitable for bleaching unified cellulose products made or manufactured from vegetable or related materials, such as regenerated cellulose sheeting sold under the trade-mark Cellophane.

From the results of my experiments, I have found that variations in strength and concentration of the added chemical may be made over a rather wide range depending upon the type of goods being treated and upon their previous history and treatment. Further, it will be understood that although I have specifically illustrated the improved bleaching process by mentioning hydrogen peroxide, I have found that certain other chemicals developing active oxygen in such solutions may be used by making the proper substitution, due regard being had for the quantity of available oxygen. As materials suitable for such substitution I may mention sodium peroxide and the per salts such as'perborates, percarbonates, persilicates and persulfates among others. It will be noted that I have illustrated bleaching solutions so high in alkalinity and peroxide that were such solutions used in the present methods of bleaching cellulose it would be injured to such an extent as to render it commercially valueless if it were not actually destroyed. Prolonged circulation of such solutions over or contact of the goods with solutions of the high concentrations of alkali that I recommend is to be avoided as by saturating the goods to produce the damp condition. I have suflicient active bleaching solution in contact therewith to carry the bleaching action to the desired point at room temperature without the dangers to which excess of such reagents would subject the fibers.

It is preferred to employ the high concentrations of alkali in cold peroxide bleaching, according to the present invention, in combination with high concentrations of peroxide as claimed in my co-pending application referred to above. Beneficial results are also secured, however, with normal concentrations of peroxide.

The term room temperature is used herein to describe a range of temperature normally encountered in a plant and may be as high as F. Where such high temperatures are encountered, the time of steeping will be less than that required at lower temperatures in order to obtain a full or standard white. -Where the term high concentration of peroxide is used, a concentration of peroxide is meant wherein the amount of peroxide, calculated as hydrogen peroxide, is greater than about 1% of hydrogen peroxide. The term moist condition or damp condition means a condition where the goods contain at least 50% by weight of liquid but are not immersed in the liquid.

I claim:

1. A composition for bleaching cellulose comprising hydrogen peroxide and a quantity of alkali equivalent to 10 to 60 grams of sodium hydroxide per liter.

2. A composition for bleaching cellulose comprising hydrogen peroxide and 10 to 60 grams oi caustic soda per liter.

3. A composition for bleaching cellulose comprising at least 1% hydrogen peroxide and a quantity of alkali equivalent to 10 to 60 grams of caustic soda per liter.

4. A composition for bleaching cellulose comprising at least 1% hydrogen peroxide and 10 to 60 grams of caustic soda per liter.

5. The process of bleaching cellulose which 5 comprises saturating cellulose with 'a bleaching solution comprising peroxide and a quantity of alkali equivalent to to 60 grams of caustic soda per liter, eliminating the excess of the bleaching solution from the cellulose so that the 0 cellulose is damp, thereafter stacking the cellulose to maintain the same damp, and permitting the cellulose to bleach in the damp condition.

6. The process of bleaching cellulose which comprises saturating cellulose with a bleaching' solution comprising peroxide and 10 to grams permitting the cellulose to bleach in the damp condition.

'7. The processof bleaching cellulose which comprises saturating celulose with a bleaching a solution comprising 1% peroxide and 10 to 60 grams of caustic soda per liter, eliminating the excess of the bleaching solution from the cellulose so that the'cellulose is damp, thereafter stacking the cellulose to maintain the same damp,

and permitting the cellulose to bleach in the damp condition.

8. The process of bleaching cellulose which comprises saturating cellulose with a bleaching solution comprising 1% peroxide and a quantity of alkali equivalent to 10 to 60 grams of caustic soda per liter, eliminating the excess of the bleaching solution from the celluose so that the cellulose is damp, thereafter stacking the cellulose to maintain the same damp, and permitting the cellulose to bleach in the damp condition. I

9. A composition for bleaching cellulose comprising hydrogen peroxide, a quantity of alkali equivalent to 19 to 60 grams of sodium hydroxide per liter and a material for stabilizing the hydrogen peroxide.

10. A composition for bleaching cellulose comprising a material liberating hydrogen peroxide and a quantity of alkali equivalent to 10 to 60 grams of sodium hydroxide per liter.

11. The process of bleaching cotton goods which comprises treating the same with a concentrated alkali solution so that the solution in the goods contains a quantity of alkali equivalent to 10 to 60 grams of sodium hydroxide per liter, incorporating a peroxide in the goods and permitting the goods to bleach while maintaining 50% to by weight of solution in the goods.

HANS O. KAUFFMANN. 

